1. Field of the Invention
This invention relates to a water repellent for window panes of automobiles and a method of repelling water on window panes of automobiles and, more particularly, to a water repellent for window panes of automobiles, which can be properly used in the rain and can form a uniform film having an excellent repellency and durability of repellency on the panes, and a simple method of repelling water on window panes of automobiles by providing the panes with water repellency through an easy operation.
2. Description of Related Art
Hitherto, a treating agent mainly comprised of a surfactant has been used in combination with a mechanical water droplets-repelling means such as a wiper, in order to eliminate glare by an oil film or poor visibility by a non-uniform water film, which is formed in the rain on window panes of automobiles. The thus used treating agent is in general called a "treating agent of a hydrophilic type".
However, when glass panes are treated with a prior art treating agent of a hydrophilic type, there is a problem that no good visibility can be secured in the panes, because images through the panes are warped by unevenness in a thickness of water film on the panes caused by wind pressure when automobiles run, particularly at a high speed in the rain. Furthermore, there is also a problem that the treating agent-coating effect is not durable for a long period not only when automobiles run at a high speed.
On the other hand, there have been proposed some methods of securing good visibility by treating window panes to provide the surface of the panes with water repellency, so that rain droplets are prevented from adhering onto the panes when the droplets come in contact with the surface of the panes. Treating agents used in these proposed methods are called of a hydrophobic type. As the treating agent of a hydrophobic type are known, for example, a water-repelling agent comprising an alkyl polysiloxane and an acid (JP-B-50-15473), an water-repelling agent comprising a siloxane oligomer, organic solvent and metal halide (JP-A-55-9652), a water-repelling agent comprising a chlorine atom-containing siloxane compound (JP-A-55-23167), JP-A-55-78080 and JP-A-55-90580), a water-repelling agent for window panes of automobiles containing an amino-modified silicone oil and a surfactant (JP-A-5-301742).
However, the water-repelling agent comprising an alkyl polysiloxane and an acid, the water-repelling agent comprising a siloxane oligomer, an organic solvent and metal halide and the water-repelling agent comprising a chlorine atom-containing siloxane compound are in general of an organic solvent type. These agents can provide excellent water repellency only when coated on glass panes in a dry state. Treatment with these agents requires such a complicated working process that the agents are coated on panes and then wiped off with a dry waste cloth or the panes are polished. Furthermore, the water-repelling agent comprising a chlorine-containing siloxane compound has a problem that it is poor in stability when stored.
Since the water-repelling agent comprising an amino-modified silicone oil and a surfactant is of an aqueous solution type, it may be used in the rain with insufficient durability and uneven effect of water repellency, partial glare and poor visibility by water droplets.
This invention has been attained under the circumstances above.